Jou Yingtzy, Wang Ya-Ling, Yen Hungchen Emilie
Department of Life Sciences, National Chung Hsing University, Taichung 40227, Taiwan.
Funct Plant Biol. 2007 May;34(4):353-359. doi: 10.1071/FP06269.
The halophyte Mesembryanthemum crytallinum L. (ice plant) is marked by giant epidermal bladder cells (EBC). The differentiation of pavement cells into EBC occurs at an early developmental stage. EBC occupy most of the surface area in the aerial parts of salt-stressed mature ice plants. A large vacuolar reservoir for ion and water storage plays an important role in salinity adaptation. To monitor the acidity of the vacuole at different developmental stages of EBC, peels from the abaxial surface were stained with a pH-sensitive dye, neutral red (NR). Presence of both NR-stained (acidic) and NR-unstained (neutral) EBC were found at the juvenile stage in ice plants. Continuous exposure to illumination decreased the acidity of the NR-stained cells. The EBC protein profile illustrated the prominent co-existence of highly acidic and basic proteins in these specialised cells. Major proteins that accumulate in EBC are involved in photosynthesis, sodium compartmentalisation, and defence. Numerous raphide crystals were found in well fertilised ice plants. Salt-stressed cells exhibited changes in the surface charge and element composition of raphide crystals. A disappearance of potassium in the high-salt grown crystals suggests that these crystals might serve as a potassium reservoir to maintain the Na/K homeostasis in this halophyte.
盐生植物冰叶日中花（Mesembryanthemum crytallinum L.）以巨大的表皮膀胱细胞（EBC）为特征。扁平细胞向EBC的分化发生在发育早期。在盐胁迫的成熟冰叶日中花地上部分，EBC占据了大部分表面积。一个用于储存离子和水分的大型液泡库在盐分适应中起着重要作用。为了监测EBC不同发育阶段液泡的酸度，用pH敏感染料中性红（NR）对叶背的表皮进行染色。在冰叶日中花的幼年期，发现了同时存在NR染色（酸性）和未染色（中性）的EBC。持续光照会降低NR染色细胞的酸度。EBC蛋白质谱表明，在这些特化细胞中，高酸性和碱性蛋白质显著共存。在EBC中积累的主要蛋白质参与光合作用、钠区室化和防御。在施肥良好的冰叶日中花中发现了大量针晶。盐胁迫细胞的针晶表面电荷和元素组成发生了变化。在高盐环境下生长的晶体中钾的消失表明，这些晶体可能作为钾库来维持这种盐生植物的Na/K稳态。
